Self-propelled toy vehicle having an auxiliary water jet propulsion system

ABSTRACT

A toy vehicle designed to run on land is powered, at least in part, by a water jet. If the water jet propulsion system is auxiliary to a main propulsion system, the main propulsion system may be a compressed air piston engine, in which case pressurization of the air supply for the piston engine and pressurization of the water tank that supplies the water jet may advantageously be achieved by using a common hand pump, and the waterjet propulsion system as well as a sound effects system may be linked to the motor drive shaft to achieve simultaneous actuation of the motor, the water jet, and corresponding sound effects.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention generally relates to a self-propelled toy vehicle having an auxiliary waterjet propulsion system. The auxiliary water jet propulsion system assists in propulsion and adds an element of visual interest to the moving vehicle.

[0003] The main source of propulsion may, according to a preferred embodiment of the invention, be a motor driven by a pressurized air supply. An example of such a motor is the piston-operated pneumatic engine disclosed in U.S. Pat. No. 4,329,806 (Akiyama et al.). Pressurization systems are used to: (i) force air into an air reservoir so that the air reservoir supplies a continuous stream of air to the piston engine upon cranking of the piston in the engine, and (ii) supply air to pressurize a water tank, from which water is expelled upon opening a valve that is activated by pushing the vehicle forward. Preferably, the pressurization systems are individual pressurization systems, each powered by a separate hand-pump connected to a common handle, although a shared pressurization system could also be used.

[0004] The invention also relates to the inclusion of a sound effects generator in a vehicle driven by a compressed air piston engine, and in particular to a vehicle arranged to generate engine sound effects in response to activating a spring loaded switch on the hood of the vehicle.

[0005] 2. Description of the Related Art

[0006] As indicated above, one aspect of the present invention relates generally to the inclusion of an auxiliary water jet in a self-propelled toy vehicle. This aspect of the invention is based on the concept that while waterjet propulsion is an inefficient means of propulsion for a land or air vehicle, addition of a water jet for auxiliary propulsion purposes is nevertheless advantageous because it adds an element of visual and tactile interest lacking in most toy vehicle propulsion systems. Another aspect of the present invention relates to the inclusion of a sound effects generator in a compressed air powered toy vehicle. Although electrically-powered vehicles commonly include sound effects, compressed air powered vehicles are notable for their relatively quiet operation.

[0007] With respect to the first aspect of the invention, there is very little art, if any, related to water jet propulsion in vehicles designed to operate on land or in the air rather than in the water, whether used as a main propulsion system or an auxiliary propulsion system. Instead, most of the related art concerning water jet propulsion systems is directed to water jet propulsion systems for marine vehicles. For the most part, such systems use some sort of electrical pump to create the water jet, although in copending U.S. patent application Ser. No. 09/604,076, it was proposed to use a hand-pumpoperated water tank pressurization system to create a water jet for propelling a toy submarine. The preferred embodiment of the present invention uniquely adapts the hand-pump-operated water tank pressurization system disclosed in the copending application to a non-marine vehicle, for use in connection with an auxiliary water jet propulsion system.

[0008] While there is little related art concerning use of water jet propulsion systems in non-marine vehicles, there are a number of prior patents related to compressed air propulsion systems, which in the preferred embodiment of the invention may be used as the main propulsion means for the vehicle. In fact, the preferred embodiment of the invention utilizes a modified version of the piston-operated pneumatic engine disclosed in U.S. Pat. No. 4,329,806 (Akiyama et al.). In the engine disclosed in the Akiyama et al patent, a piston situated in a cylinder is connected to a cam positioned on the output shaft ofthe engine, and the cam operates a valve that opens and closes to alternately place the piston in fluid communication with a continuous supply ofcompressed air, movement of the piston further placing the cylinder in fluid communication with an exhaust port, thereby providing a highly efficient and reliable two-stroke engine cycle that provides sufficient motive power to move a toy vehicle or airplane at scale speeds corresponding to those of the real vehicles they are designed to emulate.

[0009] One disadvantage of an air piston engine of the type disclosed in the Akiyama et al. patent, at least for purposes of propelling a toy, is that the air piston engine lacks the noise and visual effect of an internal combustion engine. While the compressed air piston engine can achieve scale speeds that exceed or are comparable to those of, for example, the fastest drag racers, they lack the exhaust flames and smoke, and the roar of the engine, that provide visual clues as to the speed of the vehicle. The addition of a visual reference against which the speed of the vehicle can be judged, as well as sound effects that duplicate the feel of a real drag race, can greatly enhance the experience provided by playing with such a vehicle.

[0010] Although the preferred embodiment of the present invention uses compressed air piston engine in which the cylinder intake valve is operated by cam connected to the crankshaft, similar in this respect to the engine disclosed in the Akiyama et al. patent, the present invention in its broadest form is not limited to a particular main propulsion system, and in particular is not limited to a particular type of compressed air engine. For example, compressed air piston engines that could potentially be substituted for the piston-operated pneumatic engine of the preferred embodiment include those disclosed in U.S. Pat. Nos. 6,006,517 (Kownacki et al.), 3,050,904 (Morse) 2,545,586 (Pollak), 1,796,157 (Moore) and 819,653 (Hawke). Furthermore, other types of compressed fluid powered vehicles that could be used in connection with an auxiliary waterj et propulsion system according to the principles of the present invention include the air jet and air turbine engines disclosed in U.S. Pat. Nos. 5,499,940 (Johnson et al.), 3,950,889 (Dabney), 3,789,540 (Convertine et al.), 2,943,417 (Greenspan et al.), 2,410,682 (Richardson), 2,115,556 (Maniscalco). Of course, none of these patents discloses a piston-operated pneumatic engine, or any other type ofpneumatic engine, in combination with a fluid jet propulsion system.

[0011] A prior patent that may be of interest as background with respect to the present invention is U.S. Pat. No. 3,577,677 (Bennett), which discloses what is referred-to as an “auxiliaryjet propulsion means” for a vehicle. However, unlike the present invention, the jet propulsion means disclose in the Bennett patent is not auxiliary to a main source of motive power within the vehicle, but rather to gravity, the “auxiliary” fluid jet only being activated when the vehicle is moving down a slope and passes over a projection arranged to unplug the pressurized fluid output. In addition, there is not indication that the vehicle of Bennett can use water rather than air as the pressurized fluid for the auxiliary fluid jet.

[0012] U.S. Pat. No. 5,474,486 (Chilton et al.) may also be of interest as background related art for its disclosure of a vehicle that combines a “water jet” with an electric motor. The distinction between the vehicle of the present invention and that of Chilton et al. is the waterjet of Chilton et al. is arranged to be directed at other objects orpersons and in no way resembles, or is used as, a propulsion system. Further, since the main propulsion system of Chilton et al. is electric, as is the pump that supplies the water jet, the propulsion system and water jet cannot share a compressed air supply as the source of motive power.

[0013] Turning to the sound effects aspect of the present invention, none of the patents cited above for their disclosures of compressed air engines includes sound effects. For the most part, compressed air engines operate relatively quietly, and none makes sounds corresponding to those of an internal combustion engine, much less sounds which are synchronized with starting or running of the engine. To the contrary, one of the reasons for using an air powered vehicle is to eliminate the need for an electrical system that could be used to provide sound effects. Of the above-cited patents, the only one that discloses a vehicle having both a compressed air engine and an electrical system is U.S. Pat. No. 3,050,904 (Morse), and the electrical system disclosed in the Morse patent is only used for operating lights.

SUMMARY OF THE INVENTION

[0014] It is accordingly a first objective of the invention to provide a self-propelled toy vehicle having dual power sources, one of which serves as a primary source of motive power and the other of which offers additional visual effects to provide an enhanced impression of speed and motion.

[0015] It is a second objective of the invention to provide a self-propelled toy vehicle having an auxiliary source of motive power that provides enhanced visual effects.

[0016] It is a third objective of the invention to provide a self-propelled toy vehicle having an auxiliary source of motive power that provides enhanced visual and sound effects.

[0017] It is a fourth objective of the invention to provide a non-marine vehicle having a water jet propulsion system.

[0018] It is a fifth objective of the invention to provide a vehicle having air driven main and auxiliary propulsion systems pressurized by separate hand pumps connected to a common handle.

[0019] It is a sixth objective of the invention to provide a vehicle having a compressed air motor and an auxiliary water jet propulsion system supplied with air by individual pressurization systems powered by separate hand pumps connected to a common handle.

[0020] It is a seventh objective of the invention to provide a vehicle having a compressed air motor and an auxiliary waterjet propulsion system that in which starting of both the motor and the water jet is achieved by rotating the rear axle of the vehicle.

[0021] It is a eighth objective of the invention to provide a toy land vehicle having a valve-operated auxiliary water jet propulsion system in which the valve is opened by manually pushing the vehicle, and in which the valve is closed upon operating a hand Pump used to pressurize the water supply.

[0022] It is a ninth objective of the invention to provide a toy vehicle having a compressed air motor, and that provides engine sound effects at any time by pressing down on a hood mounted button.

[0023] It is a tenth objective of the invention to provide a self-propelled toy vehicle having an auxiliary power source that provides enhanced visual effects, and a sound system that provides enhanced aural effects.

[0024] These objectives are achieved, in accordance with the principles of a preferred embodiment of the invention, by providing a toy vehicle having a compressed air piston engine, a pressurized air reservoir which supplies a continuous stream of air to the piston engine upon cranking of a piston in the engine, and a water reservoir connected a second air inlet which is pressurized upon supply of air to the water reservoir including an outlet valve that opens upon cranking of the piston in the engine to permit expulsion of water from the reservoir simultaneously with operation of the engine.

[0025] According to a preferred embodiment of the invention, pressurization of the air supply for the piston engine and pressurization of the water tank that supplies the water jet is achieved by using a common handle connected to two air pumps. The piston engine includes a single cylinder and a cam shaft driven by the piston for operating a cylinder intake valve that periodically connects the pressurized air supply with the cylinder. Starting of the engine is achieved by turning the cam shaft, for example by turning the wheels of the vehicle in case the vehicle is a land vehicle, so as briefly open the intake valve. Turning of the wheels of the vehicle also releases a waterjet valve actuator lever that maintains the valve in an open position until closed by operation ofthe hand pumps.

[0026] Although the preferred embodiment of the invention combines an air piston engine with a waterj et, the invention is intended to encompass any toy vehicle that expels water so that it at least appears to be propelled by the jet of water. Further, although the preferred embodiment of the invention uses a pressurized air water jet similar to that disclosed in U.S. patent application Ser. No. 09/604,076, it is not intended to be limited to a particular type of water jet and, insofar as the invention concerns the inclusion of a main engine, it is not intended to be limited to a particular type of main engine. Examples of alternative water jet systems that may be used in an auxiliary water jet propulsion system according to the principles of the invention include electrical pump and bladder type systems, while examples of motors that may be combined with the auxiliary water jet include electrical motors, internal combustion engines, air jet or air turbine engines, and alternative piston engines such as the piston engine disclosed in U.S. Pat. No. 6,006,517 (Kownacki et al.) which replaces the cam shaft with a valve rod connected directly to the piston.

BRIEF DESCRIPTION OF THE DRAWINGS

[0027]FIG. 1 is a cross-sectional side view of a pneumatically powered vehicle having an auxiliary water jet propulsion system according to the principles of a preferred embodiment of the invention, taken along centerline A-A in FIG. 2.

[0028]FIG. 2 is a plan view of the preferred vehicle, with air tank, water tank, and top half of the body removed.

[0029]FIG. 3 is a a cross sectional plan view of the compressed air piston engine used in the vehicle of FIGS. 1 and 2.

[0030]FIG. 4 is a cross-sectional side view of the compressed air piston engine of FIG. 3, taken along the centerline of the piston cylinder.

[0031]FIG. 5 is a cross-sectional side view of the compressed air piston engine of FIG. 3, taking along the center line of a cam actuated air valve.

[0032]FIG. 6 is an exploded isometric view of the preferred vehicle.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0033]FIGS. 1, 2, and 6 illustrate a toy vehicle having a compressed air piston engine and an auxiliary water jet constructed in accordance with the principles of a preferred embodiment of the invention, while FIGS. 3-5 illustrate details of a compressed air piston engine used in the vehicle of FIGS. 1, 2, and 6.

[0034] As illustrated in FIGS. 1, 2, and 6, the preferred vehicle includes a vehicle body 1 shaped to resemble that of a race car and secured to a base or chassis 2 by screws or other suitable attachment means (not shown). Attached to the rear of the vehicle body 1 by screws or other suitable attachment means (not shown) is a rear housing 8. All of the various parts of the preferred embodiment are primarily supported by the chassis 2, with the upper body 1 and rear housing 8 being placed on the chassis following assembly of the various subsystems of the preferred vehicle, including a pressurization system, the air and water storage systems, the air engine, and the waterjet valve assembly.

[0035] Although the shape of all of the exposed parts are consistent with parts of an actual race car, it will be appreciated by those skilled in the art that the shape of the body and other exposed parts need not be limited to those of a race car, but rather that the vehicle could have any desired shape, including but not limited to cars, trucks, planes, trains, space ships, and any other real or imaginary vehicle, and that the vehicle could even be shaped to resemble animate or inanimate objects not normally associated with vehicles. In addition, those skilled in the art will appreciate that such details as the materials of the various parts, the types of fasteners used, the construction and number of the parts which make up the body, and the configuration of any appurtenances, all may be varied without departing from the scope of the invention.

[0036] The vehicle of the preferred embodiment utilizes a rear wheel drive, although a front wheel drive could be substituted. As illustrated, the front tire/wheel assemblies 3 are rotatably secured to the chassis by screws or any other equivalent means (not shown), such as an axle, while rear wheels 5 and tires 6 are mounted on an axle 52 which includes a drive gear 45 having a carn 83 to be described in more detail below. As with the vehicle body, the wheels or tires may have any configuration appropriate to the type of vehicle, and may include configurations with more or less than four wheels, and configurations in which the wheels are hidden.

[0037] Since the preferred vehicle operates on compressed air, a pressurization system is required. The pressurized air could, within the scope of the invention, be supplied by an external source, but the illustrated embodiment uses a manual pump to pressurize the compressed air engine and auxiliary water jet systems. In particular, as shown in FIGS. 1 and 2, the air and water supply pressurization system includes a manual pump in the form of a generally U-shaped handle assembly 16, one end of which extends from the lower front end ofthe vehicle and is arranged to be grasped by the user's hand. The three legs of the U-shaped handle assembly 16 include two inner tubes 73 slidable in two outer tubes 17 mounted on the chassis 2, and two plungers 78 which extend into the outer tubes. The third leg is in the form of a t-bar 75 having a fork 59, as described below, for shutting off the water jet outlet valve to enable system pressurization.

[0038] The pump tube check valves include respective housings 44 arranged to seal and fit over the end of pump tubes 17. The check valves at the ends of the arms of the “T” serve as intake valves through which air is supplied to the air storage tank and the water storage tank, and further serve to isolate the pressurized air supply from the water jet system and air motor system. The respective air and water intake valve structures include stoppers and springs situated in passages connected respectively to the air tank inlet 42 and the water tank inlet 43.

[0039] As also shown in FIG. 1, the air/water storage subsystem of the preferred vehicle includes an air tank 18 and a water tank 19 connected to the pressurization system by tubes 40, and to the air engine and waterjet subsystems by respective air tank and water tank connections.

[0040] Water tank 19 includes a threaded filler neck, through which water may be added to the tank, an internally threaded cap 25, a strainer tube 20, a seal 24 and tether 22 secured to the cap by a screw or other appropriate securing means, and any appropriate anchor 21 tied to the tether 22 and having a dimension larger than the largest dimension of the opening in water tank 19 for preventing the cap 25 from becoming disassociated from the vehicle as the water tank is being filled. Extending from the bottom of water tank 19 is a neck onto which a clamp 80 is fitted, the connection being sealed by an oring seal. A passage in the neck 30 communicates with a passage arranged to provide water to the valve/nozzle assembly 31 described in detail below. Those skilled in the art will appreciate that although air tank 18 is illustrated as a rigid tank, it is also possible to nclude an expandable tank or bladder-type reservoir.

[0041] As shown in detail in FIGS. 3-5, the preferred compressed air engine includes separate intake valve and cylinder chambers connected by a tube 40 and crank shaft 51. Pressurized air is supplied to a pneumatic piston engine that includes an intake valve 87 having an inlet and outlet opening, a ball 38, and a steel pin 56 situated in a passage between the outlet and the inlet. Opening of the intake valve 87 is caused by a cam follower pin 69 that retracts ball 38 upon rotation of cam 86 to a predetermined position. Retraction of ball 38 permits passage of air through the outlet opening to a connecting tube 40. Connecting tube 40 supplies air through an air cylinder inlet to air cylinder 88, which includes a piston 48 connected to a connecting rod 47, and which in turn is connected by a pin 49 to crank 50 mounted on crank shaft 51. Crank shaft 51 also is connected to drive gear 46. Drive gear 46 engages axle gear 45 on the axle to drive the rear wheels.

[0042] In operation, upon opening of engine intake valve 87, air entering the air cylinder 88 causes piston 48 to move away from the entrance opening toward the end of the cylinder, thereby causing connecting rod 47 to turn crank 50 and crank shaft 51 by approximately 180°. This causes cam 86 to rotate by a corresponding amount and in turn causes ball 38 to shut off supply of air to the air cylinder 88. Continued rotation of the crank shaft 51 in response to movement of the vehicle completes rotation of the crank and returns piston 48 to its initial position. Piston seal 53 is arranged such that air is exhausted past the piston seal during the return stroke, at which time cam 86 also completes rotation to a position at which the intake valve is again opened. Opening of intake valve 67 causes pressurized air to again be supplied to the air cylinder 88 to move piston 48, completing the engine cycle. Preferably, cam 86 is designed such that the valve is only open for a brief period at the top of the stroke, although the timing of the engine cycle may of course be varied depending on the desired engine performance.

[0043] The illustrated engine may initially be started by manually rolling the vehicle to rotate rear wheels 6 and axle 52, in turn causing rotation of cam 86. Rotation of cam 86 causes opening of intake valve 87, and consequent supply of air to the air cylinder 88, thereby initiating the power cycle described above.

[0044] It will be noted by those skilled in the art that operation of the preferred engine is similar to that of U.S. Pat. No. 4,329,806 (Akiyama et al.) in its use of a cam driven intake valve, but differs structurally in its use of separate intake valve and air cylinder structures. As explained above, it is nevertheless within the scope of the invention to substitute the specific engine structure described in the Akiyama patent for the illustrated pneumatic piston engine structure, or to substitute other pneumatic engine structures such as the one described in U.S. Pat. No. 6,006,517 (Kownacki et al.).

[0045] The auxiliary water jet system of the preferred vehicle, illustrated in detail in FIGS. 1 and 2, includes a water jet valve positioned at the rear of the vehicle and designed to be opened upon manual rolling of the vehicle, as described above, simultaneously with starting of the compressed air engine. To this end, the water jet valve is opened and closed by a lever actuator 83 operatively connected to axle 52, which is rotated to start the engine.

[0046] More specifically, the waterjet valve is contained in a nozzle 7 connected to the water tank 19. An interior passage communicates with an outlet opening arranged to be closed by a stopper consisting of a poppet 33 and a valve shaft 26. Valve shaft 26 extends through an opening in nozzle 7, which is sealed by an o-ring. As a result, movement of cam 83 causes thepoppetvalveto open, releasing ajet ofpressurized water from water tank 19 through nozzle 7. As a result, the preferred embodiment provides a system in which the waterjet is activated simply by manuallypushing the vehicle to open the water jet valve, and in which the jet valve is closed to permit refill and repressurization simply by operating the hand pump used to pressurize the water supply.

[0047] Finally, as best shown in FIG. 1, the compressed air powered vehicle of the preferred embodiment of the invention includes a sound module 63, and a manual switch actuator 12 arranged to resemble the upper portion of the engine of the vehicle. While the nature of the sounds generated by sound module 63 is entirely optional, those skilled in the art will appreciate that the sound module may be arranged, by way of example and not limitation, to generate engine starting sounds through a speaker when switch 12 is depressed. Alternatively, by way of further example, the engine sounds may be synchronized to or actuated by movement of the pump handle, or of any other movable part on the vehicle.

[0048] Although various preferred embodiments of the invention have been described with sufficient particularity to enable a person skilled in the art to make and use the invention without undue experimentation, it will be appreciated that numerous other variations and modifications ofthe illustrated embodiments, in addition to those already noted above, may be made by those skilled in the art. Each of these variations and modifications, including those not specifically mentioned herein, is intended to be included within the scope of the invention, and thus the description of the invention and the illustrations thereof are not to be taken as limiting, but rather it is intended that the invention should be defined solely by the appended claims. 

What is claimed is:
 1. A toy vehicle, comprising: a compressed air motor arranged to provide a main motive force by driving at least one wheel of the vehicle to move the vehicle in a first direction; and an auxiliary water jet propulsion system arranged to direct a water jet in a direction opposite the first direction.
 2. A toy vehicle as claimed in claim 1, wherein the auxiliary propulsion system comprises: a water tank; a water tank pressurization subsystem for supplying air to the water tank in order to pressurize the water tank; a nozzle arranged to direct a jet of water in a rearward direction to thereby cause said vehicle to move in a forward direction; a valve connected between the air inlet and the nozzle, wherein when said valve is closed, water is prevented from being supplied to said nozzle, and wherein when said valve is open, water is supplied under pressure from said water tank to said nozzle; and a valve actuator lever arranged to open said valve in response to move of said vehicle.
 3. A toy vehicle as claimed in claim 2, wherein said valve actuator lever is mounted on a chassis of the toy vehicle, and said toy vehicle further comprises a release lever arranged to retain said valve actuator lever in a valve-closure position, at least two wheels connected by an axle, a cam arranged to cause said release lever to disengage from said valve actuator lever is response to movement of said axle, causing said valve actuator lever to move to a valve-opening position upon movement of said axle and release by said release lever.
 4. A toy vehicle as claimed in claim 3, wherein said water tank pressurization subsystem is a hand pump, and wherein said hand pump includes an extension arranged to return said valve actuator lever to said valve-closure position upon operation of said hand pump.
 5. A toy vehicle as claimed in claim 2, wherein said water tank pressurization subsystem is a hand pump.
 6. A toy vehicle as claimed in claim 2, wherein said water tank pressurization subsystem is further arranged to supply air under pressure to an air tank, said air tank being arranged to supply pressurized air to said compressed air motor.
 7. A toy vehicle as claimed in claim 6, wherein said water tank pressurization subsystem includes a hand pump.
 8. A propulsion system as claimed in claim 1, wherein said compressed air motor is a compressed air piston engine.
 9. A toy vehicle as claimed in claim 8, wherein said compressed air piston engine comprises: an intake valve connected to a source of pressurized air; an air cylinder connected to receive pressurized air from said source through said intake valve when said intake valve is in an open position; a piston within said air cylinder; a connecting rod extending from said piston; a crank connected to the connecting arm; a shaft connected to and rotatable with said crank; a cam connected to and rotatable with said shaft; a cam follower pin engaged with said cam and connected to said intake valve, wherein when said valve is in an open position, pressurized air is supplied to said cylinder to cause said piston to move, movement of said piston causing said connecting rod to rotate said crank, rotation of said crank causing rotation of said shaft and said cam, rotation of said cam causing said valve to move to a closed position, wherein said shaft is further connected to a drive gear arranged to cause rotation of at least one wheel of said vehicle in response to turning of said shaft to thereby move said vehicle, and wherein movement of said vehicle causes further rotation of said shaft to return to said piston to said first position and re-open said intake valve.
 10. A toy vehicle as claimed in claim 9, wherein said drive axle engages a second cam arranged to open a water jet outlet valve in said water propulsion system.
 11. A toy vehicle as claimed in claim 9, wherein said intake valve and said air cylinder are separate structures connected by a first air hose.
 12. A toy vehicle as claimed in claim 11, wherein said intake valve is a check valve positioned in a passage having an inlet connected to a second air hose, said second air hose being connected to an air tank, and an outlet connected to said first air hose.
 13. A toy vehicle as claimed in claim 1, wherein said air motor and said water jet propulsion system are arranged to be started simultaneously.
 14. A toy vehicle as claimed in claim 13, wherein said air motor and said water jet propulsion system are arranged to be started upon manual pushing of said vehicle.
 15. A toy vehicle as claimed in claim 14, wherein said manual pushing of said vehicle causes an intake valve of said air motor and an outlet valve of said water jet propulsion system to open.
 16. A toy vehicle as claimed in claim 1, further comprising a sound module having a switch arranged to be actuated upon pressing down on a part resembling an engine projecting through a hood of the vehicle.
 17. A propulsion system for a toy vehicle, comprising: a water tank; a water tank pressurization subsystem for supplying air to the water tank in order to pressurize the water tank; a nozzle arranged to direct ajet of water in a rearward direction to thereby cause said vehicle to move in a forward direction; a valve connected between the air inlet and the nozzle, wherein when said valve is closed, water is prevented from being supplied to said nozzle, and wherein when said valve is open, water is supplied under pressure from said water tank to said nozzle; and a valve actuator lever arranged to open said valve in response to move of said vehicle.
 18. A propulsion system as claimed in claim 17, wherein said valve actuator lever is mounted on a chassis of the toy vehicle, and said toy vehicle further comprises a release lever arranged to retain said valve actuator lever in a valve-closure position, at least two wheels connected by an axle, a cam arranged to cause said release lever to disengage from said valve actuator lever in response to movement of said axle, to cause said valve actuator lever to move to a valve-opening position upon movement of said axle and release by said release lever.
 19. A propulsion system as claimed in claim 18, wherein said water tank pressurization subsystem is a hand pump, and wherein said hand pump includes an extension arranged to return said valve actuator lever to said valve-closure position upon operation of said hand pump.
 20. A propulsion system as claimed in claim 17, wherein said water tank pressurization subsystem is a hand pump.
 21. A propulsion system as claimed in claim 17, further comprising a compressed air motor arranged to provide a main motive force for moving said vehicle, said jet of water providing an auxiliary motive force.
 22. A propulsion system as claimed in claim 21, wherein said water tank pressurization subsystem is further arranged to supply air under pressure to an air tank, said air tank being arranged to supply pressurized air to said compressed air motor.
 23. A propulsion system as claimed in claim 22, wherein said water tank pressurization subsystem includes a hand pump.
 24. A propulsion system as claimed in claim 21, wherein said compressed air motor is a compressed air piston engine.
 25. A compressed air piston engine, comprising: an intake valve connected to a source of pressurized air; an air cylinder connected to receive pressurized air from said source through said intake valve when said intake valve is in an open position; a piston within said air cylinder; a connecting rod extending from said piston; a crank connected to the connecting arm; a shaft connected to and rotatable with said crank; a cam connected to and rotatable with said shaft; a cam follower pin engaged with said cam and connected to said intake valve, wherein when said valve is in an open position, pressurized air is supplied to said cylinder to cause said piston to move, movement of said piston causing said connecting rod to rotate said crank, rotation of said crank causing rotation of said shaft and said cam, rotation of said cam causing said valve to move to a closed position, wherein said shaft is -further connected to a drive gear arranged to cause rotation of at least one wheel of said vehicle in response to turning of said shaft to thereby move said vehicle, and wherein movement of said vehicle causes further rotation of said shaft to return to said piston to said first position and re-open said intake valve.
 26. A toy vehicle as claimed in claim 26, wherein said intake valve and said air cylinder are separate structures connected by a first air hose.
 27. A toy vehicle as claimed in claim 27, wherein said intake valve is a check valve positioned in a passage having an inlet connected to a second air hose, said second air hose being connected to an air tank, and an outlet connected to said first air hose. 